In this 1999 Warner Brothers animated feature, the Siamese characters are drawn with fair skin and slanty eyes.
Thais typically have darker skin and larger eyes compare to East Asians. While many modern urban Thais are light-skinned or narrow-eyed because of intermarriage with Chinese, shouldn't the animated feature represent those natives who are dark-skinned and wide-eyed too? Perhaps this is another case of the "all Asians look the same" syndrome.
The servant girl who happens to be the prince's love interest has blue eyes. This is clearly inaccurate in a Southeast Asian setting. This follows a pattern in U.S. cartoons where the "specialness" of a character is established by giving him/her/it blue eyes. The Lion King's love interest in Disney's Lion King and Mulan's heroic steed in Disney's Mulan both have blue eyes. And these animals commonly do not have blue eyes.
Also, there is the use of a gong with a Chinese-looking dragon symbol. Last I checked with a native Thai, the Chinese dragon is not a Siamese symbol. Sigh. Again, the "all Asians do the same things" syndrome.
On the plus side, the Siamese prince is presented as a lady's love interest, and at least departs from the Western stereotype of the unattractive, wimpy Oriental male.